In the prior art, various attempts have been made to provide a line-of-sight measuring system having the requisite simplicity so as to enable the use thereof in conjunction with a computer. The concept of a retroreflector which will reflect incident light back in the direction from where it came, is well known in the art. Applicant is aware of the following United States Patents, each of which teaches the concept of a concave reflector:
U.S. Pat. Nos. 1,966,792; 3,923,382; Re. 19070; 2,120,524; 2,273,847; 2,921,305. It is noted, however, that none of these patents teaches or suggests any of the concepts of the present invention other than the concept of a concave focusing retroreflector per se as taught in U.S. Pat. No. 3,923,382.
The following patents are also known to Applicant and are believed to be only generally related to the present invention:
U.S. Pat. No. 3,759,614 to Harvey discloses a device for determining the range from a camera to an object which is to be photographed. The device includes a light source which must be directed toward the target and further includes a sensor in the camera which determines the intensity of the received light to thereby enable the automatic focusing of the camera. The Harvey system is significantly different from the present invention in that the light source of Harvey is moved along with the camera in an aiming manner whereas in the present invention, the light source remains stationary during the entire operation thereof. Further, the Harvey device measures distance by measuring intensity of received light and does not measure the line-of-sight nor does the Harvey device translate the line-of-sight to cursor movement on a computer screen. A further difference resides in the fact that the Harvey device does not use a focusing reflector attached to the object which is to be photographed.
U.S. Pat. No. 3,885,872 to Howe, Jr., et al. discloses a digital proximity sensing system which utilizes a light source and a pair of photo-sensitive transducers. The device disclosed by Howe, Jr., et al. only measures the distance to an object and not the line-of-sight. The Howe, Jr., et al. device requires the use of two photosensors whereas in the present invention a single position sensing detector is utilized. The system does not use a focusing reflector attached to the target, includes no disclosure of translation of line-of-sight to cursor movement on a computer screen and does not contemplate movement of the target.
U.S. Pat. No. 4,207,002 to Gara, et al. discloses an apparatus for detecting an output image of an optical correlation which basically measures the dimensions of an object which is not moving. The Gara, et al. device illuminates the target from behind with a coherent light source which is different from the present invention which uses a passive focusing reflector to reflect light from a light source back to a position sensing detector adjacent to the light source.
U.S. Pat. No. 4,309,618 to Carter, Jr., et al. discloses an optical distance measurement device which merely finds the range to an object. The device relies upon the magnitude of the light received to determine the range, whereas in the present invention, no such measurement is made. In fact, in the present invention, the intensity of the light received is not taken into account whatsoever in the determination of the line-of-sight.
U.S. Pat. No. 4,313,654 to Matsui, et al. discloses an automatic range finder system for a photographic camera including light emitting and receiving means. The Matsui, et al. invention utilizes a number of zones of distance from the camera and determines which particular zone the target is located in to thereby cause the circuitry within the camera to automatically focus the camera so that any target within the particular zone is in focus. Of course, in this patent, no line-of-sight measurements are made, no translation of measurements to cursor movement on a computer screen are made, no focusing reflector is used and there is no contemplation of target movement.
U.S. Pat. No. 4,330,202 to Yokota discloses a range detecting device similar to Matsui, et al. discussed hereinabove except that no zone indication is used, the device merely measures the distance. The basic differences between the present invention and Yokota are the same as the basic differences between the present invention and Matsui, et al.
U.S. Pat. No. 4,341,447 to Biber, discloses an infrared camera ranging system which utilizes two infrared responsive sensors spaced a predetermined distance from one another on the camera body, which sense light emitted from a source of infrared light attached to the target. Of course, this is significantly different from the present invention in that the target has an active source of light whereas in the present invention a passive focusing reflector is used. The position sensors in Biber can only measure the relative angle to the target in the horizontal plane whereas in the present invention, the sensor measures the relative angle to the target in both the horizontal plane and the vertical plane. Other significant differences also exist.
U.S. Pat. No. 4,109,145 to Graf, discloses a line-of-sight detecting apparatus which produces signals indicative of the direction along which the operator's eye is gazing. A display with predetermined positions thereon is positioned for viewing by the operator and a computer receives the signals from the line-of-sight detecting apparatus and utilizing a timing function, determines when the operator's line-of-sight is directed toward one of the pre-determined positions on the display for a predetermined length of time. If the user looks at one of the targets long enough , the function correlated to that position on the target screen will be activated. There are several differences between the present invention and the invention disclosed by Graf. Firstly, in Graf, the direction at which the eye is looking is measured whereas in the present invention, in one mode thereof, the focusing reflector is attached to the person's head and the actual direction in which the head is facing is measured. Through the use of the present invention, a cursor on a computer screen is moved so as to line up with the direction in which the head is pointing. This is different from Graf, in that in Graf no cursor is moved. Rather, a fixed location on a screen is sensed so as to trigger the actuation of the function related to that position.
U.S. Pat. No. 4,340,878 to Spooner, et al. discloses a visual display apparatus which comprises a flight simulator used for pilot training. A spherical retroreflective screen is used to reflect back projected scenes to the pilot. In this invention, the spherical retroreflective screen operates only to reflect images back to the pilot for viewing and is not spherical for the purpose of focusing all incident light into one line-of-sight. It works as a true retroreflector with the reflected light being reflected parallel to the incident light and with the spherical shape of the screen giving the reflected light the maximum intensity. The screen is extremely large whereas in the present invention the retroreflector is extremely small. In Spooner, et al, the retroreflector does not move whereas in the present invention the focusing reflector moves with the target. In particular, in one application of the present invention, focusing reflector is attached to the head of the user and the line-of-sight, from the user's head with the focusing reflector attached thereto, to a point on a two-dimensional computer screen is determined and correlated with the computer screen cursor. This is completely opposite to Spooner, et al. wherein the retroreflector is separate from the head of the user.
U.S. Pat. No. 4,445,029 to Nagaoka, et al, discloses a distance detector using a photo-potentiometer and a continuous detecting system which measures the distance to an object which is to be photographed. The measurement is in zones similarly to the patent to Matsui discussed hereinabove and uses a single axis photocell. The difference between the present invention and Nagaoka are similar to the differences between the present invention and Matsui, et al.
U.S. Pat. No. 4,457,625 to Greenleaf, et al. discloses a self-calibrating contour measuring system which measures a surface over which a focusing reflector is being moved and is only used to measure curvature, does not measure line of sight and does not translate line of sight into cursor movement on a computer screen. Further, the device does not use a spherical shaped retroreflector as does the present invention.
Also known to applicant but only believed to be of general interest regarding the present invention is a publication entitled "Electronic Device Control Using the Retroreflective Concept" by Hodgetts, et al. and published in the Proceedings of International Conference on Rehabilitation Engineering - Toronto - 1980.